Gnathostoma

Gna`thos´to`ma

n. pl.

1.

(Zool.) A comprehensive division of vertebrates, including all that have distinct jaws, in contrast with the leptocardians and marsipobranchs (Cyclostoma), which lack them.

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.